1. Field of the Invention
The present invention relates to a display device equipped with color filters and, more particularly, to a transflective liquid crystal display having a transmissive region and a reflective region within each one pixel.
2. Description of Related Art
In recent years, so-called transflective liquid crystal displays (LCDs) operating in both reflective and transmissive display modes have been often used as display portions of mobile electronic devices.
A transflective LCD has both transmissive and reflective regions within each one pixel. The transflective LCD operates either in a transmissive display mode in which light transmits through transmissive regions formed in pixels or in a reflective display mode in which light is reflected by reflective regions formed in the pixels.
When the transflective liquid crystal display is used outdoors, the display is employed under bright ambient conditions. In this state, the reflective mode is added to the transmissive mode, and external light is used for display.
The reflective LCD has the problem that the visibility deteriorates severely when the external light is weak. On the other hand, the transmissive LCD has the problem that in cases where the external light is very intense (e.g., under fine weather, outdoor conditions), the visibility deteriorates.
A transflective LCD uses a display mode in which the reflective mode and transmissive mode are combined to solve the above-described problems. This kind of device is proposed, for example, in U.S. Pat. No. 6,654,076.
Many transflective LCDs use an active matrix structure in which thin film transistors (TFTs) are used as switching elements for selectively supplying a video signal to pixel electrodes.
In an active-matrix liquid crystal display, a TFT substrate on which TFTs and pixel electrodes are formed is disposed opposite to a color filter substrate on which color filters are mounted to provide a color display. A liquid crystal material is sealed in between the two substrates, thus completing the display. Plural video signal lines and plural scanning lines intersect each other on the TFT substrate. Plural regions partitioned by the video signal lines and scanning lines are arranged in a matrix. TFTs and a pixel electrode are formed in each region, forming a pixel.
In a liquid crystal display, a counter electrode is disposed opposite to pixel electrodes. An electric field is produced between each pixel electrode and the counter electrode. The orientation of liquid crystal molecule is changed by applying a voltage between the pixel electrode and the counter electrode. Concomitantly, the characteristics of the liquid-crystal layer for light is change. By making use of this property, a display is provided.
Generally, VA (vertical alignment) displays in which a counter electrode is formed on a color filter substrate and IPS (in-plan switching) displays in which a counter electrode is formed on a TFT substrate are known.
Color filters are formed on a color filter substrate in a corresponding manner to pixels to provide a color display. Each color filter transmits certain wavelengths of light. Three pixels form a unit color element of a color display. Each pixel has color filters of red (R), green (G), and blue (B).